Recently, as technology development and demand for mobile devices have increased, there has been a rapid increase in demand for secondary batteries capable of charging and discharging as energy sources, and thus a lot of research has been conducted on secondary batteries capable of satisfying various demands. In addition, the secondary battery has received attention as a power source of an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PLUG-IN HEV), etc., that are suggested as a solution to solve the air pollution of existing gasoline vehicles and diesel vehicles using fossil fuels.
Thus, an electric vehicle (EV) that is able to be operated only by a battery, a hybrid electric vehicle (HEV) that uses the battery in combination with an existing engine, etc., have been developed, and some of the vehicles have been commercially available. A nickel-metal hydride (Ni-MH) secondary battery is mainly used among the secondary battery as power sources for EV, HEV, etc. However, researches using lithium secondary batteries having high energy density, high discharge voltage, and output stability have been actively conducted, and some are in the stage of commercialization.
When the secondary battery is used as the power source of the vehicle, the secondary battery is used in the form of a battery pack including a plurality of battery modules or a battery module assembly.
However, since the battery pack for a vehicle is generally electrically connected to each device while being mounted in an internal space such as a trunk, it occupies an excessively large space in the vehicle, and thus there is a limit to fully utilizing the internal space of the vehicle.
Therefore, there is a high need for a technique capable of fundamentally solving these problems.